| Budget Amount *help |
¥7,100,000 (Direct Cost: ¥7,100,000)
Fiscal Year 2003: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2002: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2001: ¥4,800,000 (Direct Cost: ¥4,800,000)
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| Research Abstract |
Vanadium alloy (V-4Cr-4Ti) has been proposed as a structural material for fusion reactors because of its lower neutron induced activation and more rapid decay than other candidate materials and good thermal-mechanical properties in the high temperature region. One important of concern is the embrittlement of V-alloy due to oxygen and hydrogen absorption. In 2001 FY, we mainly investigated the solubility of hydrogen for the V-alloy and the suppression of hydrogen absorption by titanium oxide coatings. We found that (1) the embrittlement of V alloy with high purity due to hydrogen absorption does not occur when the operation temperature is higher than 400℃ and pressure is lower than 1 Pa, and (2) in lower operation temperature (<300℃), the embrittlement might occur during a long operation rime, and (3) the hydrogen absorption rate of T-oxide coated V alloy decreased with increase of Ti-oxide thickness at the absorption temperature of 300℃, and (4) if a dense and thick Ti-oxide film witho
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ut cracking can be coated on the surface of V-alloy, the lifetime of V-alloy might be enlarged. In 2002 FY, the deuterium retention properties of the V alloy, were mainly investigated by thermal desorption spectroscopy after deuterium ion irradiation. The deuterium ion irradiation was carried out at 110 and 500 ℃ (operation temperature of blanket made by V alloy) with ion energy of 1.7 keV We found that (1) deuterium retained in the sample was desorbed in the forms of D_2, HD, HDO and D_2O, and (2) the amount of retained deuterium at 110 ℃ increased with the ion fluence, and did not saturate to a fluence up to 1x10^<19> D/cm^2, and (3) the retained amount at 110℃ was one and two orders of magnitude larger than graphite and tungsten, respectively, and (4) the retained amount of deuterium was strongly affected by the existent of titanium-oxide segregated in the near surface region, and (5) the retained amount at 500℃ was one order of magnitude smaller than that at 110℃. In 2003 FY, deuterium ion irradiation for the V alloy was carried out at 300℃ (wall temperature of ITER) and 500℃ at higher ion fluence region. We found that (1) for the deuterium ion irradiation at 500℃, the amount of retained deuterium decreased with increase in ion fluence in the high fluence region, and (2) the amount of retained deuterium was 0.1-3% of the total deuterium ion fluence, and (3) the retained amount was almost the same as that for graphite or tungsten, and (4) since the operation temperature of V alloy blanket Is high (400-700℃), the retention amount by bath hydrogen gas and ion becomes very small. In 2003 FY, helium ion irradiation with high helium flux was also carried out for the V alloy to Investigate the retention and thermal desorption properties of helium. We found that (1) helium was desorbed around at 230℃, 530℃ and 930℃, and (2) the amount of retained helium increased with the fluence, and (3) the retained amount was saturated to a fluence up to 5x10^<18> He/cm^2. Less
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